The use of modular assemblies permits the manufacture of families of products using a common base, each personalised by different options or functions, notably complications in the case of a mechanical timepiece movement.
The concept of extremely high precision modules or cassettes allows large scale production to be combined with high quality goods.
Thus, modular sub-assemblies for timepiece movements are known, from EP Patent Application Nos 11193173.9 and 11193174.7 in the name of ETA SA. The mechanical modules disclosed in these Patent Applications are irreversibly pre-adjusted and assembled to ensure the durability of their settings.
However, in a conventional embodiment, the modules do not always allow for a reduction in the number of components, which would both reduce production costs and simplify the assembly plan, enabling mid-level technical personnel to assemble and adjust the most complex functions.
Adjusting the active length of the balance spring is conventionally achieved using an index assembly having several components, which is expensive and cumbersome.
CH Patent Application No 577194B5 in the name of Ebauches Bettlach discloses a pinning and index assembly device, wherein the index has a profiled aperture delimiting several tongues, which are at least partially bent obliquely; the balance cock has a flat annular portion surrounding the balance bearing, and the tongues of the index extend partly above and below the cock.
GB Patent Application No 705 991A in the name of Francis Atkinson discloses an aperture having inward facing resilient tongues for clamping a balance staff pin.